A numerical model of VPS for offshore wind turbine monopiles based on hypoplastic theory

Abstract

The current research on the penetration of offshore wind turbine monopiles primarily focuses on driving with a vibratory hammer, although there are several smaller studies that focus on the vibrating penetration mechanism. To further the body of research, this paper establishes a numerical model to calculate the vibration penetration speed (VPS) of an offshore wind turbine monopile that considers the soil plugging effect. In this model, a monopile is assumed to be a rigid body. The surrounding soil is divided into a series of circular cylinders of concentric axes. The shear stress at the external soil elements' interfaces and the soil's vertical stress at the monopile toe are calculated using the Gudehus–Bauer hypoplastic constitutive model. The VPS is obtained from the motion equation by compiling it in MATLAB R2012b. Finally, a finite element model is conducted to verify the results, showcasing the rationality of the proposed model. Parameter analyses are also conducted to study the influences of the soil void ratio, soil internal friction angle, vibration frequency, ratio of static load to dynamic load, and monopile diameter on VPS.